1. Field of the Invention
The present invention generally relates to coin operated systems and, more particularly, to coin escrow devices for using coin operated systems such as vending machines, coin operated telephones, and the like.
2. State of the Art
Coin operated vending systems, such as coin operated telephones, often include devices, called "escrow" devices to temporarily hold coins until such time as control signals indicate whether the coin should be returned to the system user or permanently collected. Typical escrow devices in coin operated telephones include a mechanism to release the coins to a coin box in the event that a call has been successfully placed, and a mechanism to return coins to the calling party in the event that a call is not successfully completed.
Escrow devices for coin operated vending systems needs to be reliable. An escrow device must operate to discharge all escrowed coins to a collection box only when the vending operation has been successfully completed and, conversely, must return all escrowed coins to the system user only when a vending operation has not been successfully completed. If an escrow device does not operate reliably, the vending system may be damaged by an irrate user, or revenue can be lost to the owner of the system. U.S. Pat. No. 4,782,937 describes a prior art escrow device for coin operated systems. This patent is incorporated herein by reference.
In coin operated escrow systems, jamming is a common problem. For this reason, some coin escrow devices use jam detection circuitry. In prior art systems, electro-mechanical means have been employed to detect jamming within the coin escrow hopper using contact switches. When a coin deposit is detected, a contact switch is closed to tell the control electronic module that the coin escrow has activity. When a call connection is made or fails, a gate of the escrow hopper will open to accept or return the coins, and the contact switch will be reset to an open circuit position. If the coin escrow is jammed, the contact switch will remain closed and thus give a signal to the control electronic module that there is a coin jam. The use of contact switches can cause problems, however. Contact switches are subject to breakdowns due to air corrosion, electrochemical corrosion, or for mechanical reasons. To avoid the breakdown problems common with contact switches, some escrow systems do not use coin jam detection at all.
It is desired to have an improved system to detect jams in a coin escrow device.